Ahoi Gotmilk,
on VIIC is tank #3 the middle 'Tauchzelle' (bad translation 'diving cell'
)
There are tanks to compensate torpedos, tanks to accelerate diving... but 'Tauchzellen' are for trimm...
These tanks get a valve to let the air out off the top "Vent"; or to let the Water in from the buttom "flood"; also to "blow" compressed air into them...
eg:
go Dive: both open
go Surface: 'Vent' close, 'flood' open and 'blow' out the water through the opened 'flood' with compressed air
now comes trim:
keep Periscope depth: 'vent' close, 'flood' open and the sub 'swims' under water on the pressured air inside that tank
